Method for the elimination of hanging-disturbances in shaft furnaces



Patented Aug. 18, 1936 UNITED STATES METHOD FOR THE ELHVIINATION OF HANGIN G-DISTURBAN CES IN SHAFT FURNACES Wilhelm Lennings, Oberhausen,

Wat, Grosshesselohe, near assignors, Carbide and of New York N Drawing.

2 Claims.

This invention relates to the operation of blast furnaces and has forits object the elimination of troubles due to the tendency of the chargeof such furnaces to stick or hang in the shaft.

In shaft furnaces, for example, in the produc tion of iron or phosphorusin the blast furnace or in the burning of cement clinkers, the operationis frequently violently disturbed in that the charge passes irregularlydownward through the shaft and finally hangs. In the production of iron,in order again to start up a furnace which has so hung it is customaryto blow with a colder blast after the hanging-disturbance begins. Inother instances, for example, in the production of cement, this methodcannot be employed because cold blast is ordinarily utilized from thestart. In such a cast it is usual to combat the disturbance by means ofintensely cooling the shaft walls or by briquetting the fuel togetherwith the fines of the charge.

We have discovered that such hanging disturbances in shaft furnaces canbe eliminated in a surprisingly easy manner by increasing the oxygenconcentration in the furnace blast. This discovery could in no way beforeseen because in many ways, particularly in regard to thedistribution of heat between the hearth and shaft, an enrichment of theblast with oxygen has directly opposite results from those desired.Thus, the idea of utilizing oxygen-enriched blast for the same purposesfor which hot blast is used is -well known. It has, for example, beenproposed to utilize oxygen-enriched blast in place of high blasttemperatures in those instances in which a particularly powerfulsmelting effect is required slag of the composition disturbances butrather tends to increase them, it was in no way obvious that theenrichment of the blast with oxygen, which in regard to the smeltingaction has the same effects as hot blast, would eliminate hangingdisturbances contrariwise to the eifect of hot blast.

Oxygen enrichment of the blast in accordance Y with the practice of thepresent invention has the advantage in comparison with operation utiandErnst Kar- Munich, Germany,

by mesne assignments, to Union Carbon Corporation, a corporationApplication February 4, 1935, Serial In Germany February 5, 1934 lizingordinary cold blast that while the blast heat introduced into the hearthremains approximately the same, the temperature in the hearth andconsequently the available quantity of heat are increased as compared tonormal operation. As a result there is a lessening of the dangerousconsequences of hanging, such for example as the sudden descent of theshaft contents-into the hearth whereby there may result a too intensecooling of the iron and slag in the hearth and displacement of the slagso that it comes into contact with the ore charge. Such harmfuldisturbances are decreased to a much greater extent by increasing theoxygen concentration of the blast than by the utilization of a colderblast.

The explanation for the similarity of the effects of cold blast andoxygen enrichment in the elimination of hanging disturbances may besought in the fact that both of these methods result in an increase inthe volume of oxygen passing through the blastpipe-cross section perunit of time. Naturally, it is also possible, for the elimination ofhanging difiiculties, to reduce the temperature of the blastsimultaneously with oxygen enrichment without departing from the spiritof my invention. Likewise, the utilization of oxygen enriched blast maybe limited to such period as the furnace continues to hang and thencontinuing the operation with ordinary air as furnace blast. Sometimes,however, in a furnace which operates with difficulty, it will beadvantageous to enrich the blast with oxygen continuously, in which casethe concentration of oxygen may be increased to the desired extent andfor such a period of time as may be necessary to overcome a tendency forthe charge to hang.

We claim:

1. Method of overcoming the difficulties associated with the tendency ofblast furnace charges to hang, which comprises increasing the oxygencontent of the blast until the disturbance has been corrected.

2. In a blast furnace smelting process, the

method of correcting a hanging of the charge,

of the blast, and decreasing the temperature of the blast, until theeffects of the disturbance have been eliminated.

WILHELM LENNINGS. ERNST KARWAT.

